In recent years, white blood cell adsorption devices have started to be used widely as treatment devices for inflammatory bowel disease (IBD) and rheumatoid arthritis (RA). White blood cell adsorption devices use the principles of adsorption and filtration to directly remove the white blood cells, which can cause inflammation, from the blood, and have been shown to have a therapeutic effect. The main advantage of medical treatments using a white blood cells adsorption device is that, unlike treatments using drugs, side-effects are minimal. For the white blood cell adsorption devices in current use, methods that employ a carrier having a specified surface roughness and methods that employ a filter composed of ultra-fine polymer fibers have been proposed.
For example, Patent Document 1 discloses a carrier for adsorbing granulocytes that has an irregular surface for which the center line average roughness Ra is within a range from 0.2 μm to 100 μm and the average spacing Sm between irregularities is within a range from 5 μm to 200 μm.
Further, Patent Document 2 proposes a method of producing porous beads in which at least two polymers each having a number average molecular weight of at least 10,000 but having different coagulation values are dissolved in a solvent that exhibits favorable compatibility with each polymer, and the resulting polymer solution is then added dropwise to a coagulant containing a non-solvent, thereby causing coagulation and producing porous beads.
Moreover, Patent Document 3 discloses a technique in which by aligning the fibers of an organic polymer with a high degree of regularity, namely in a substantially parallel arrangement, and then passing blood between these fibers, the white blood cells can be captured on the surface of the fibers while those problems that have proven difficult to prevent using filters formed from nonwoven fabrics or the like, such as the destruction of blood cells and the coagulation of the blood, can be overcome.
These methods have been proposed for removing mainly the white blood cells such as granulocytes and lymphocytes from the blood of patients suffering from cancer or immune system abnormalities. However, recent research has made it clear that particularly in the case of inflammatory diseases such as autoimmune disease, it is not only the white blood cells, but also the platelets within the blood, that act as inflammatory cells.